Preparation Of COFs Coated Stir Bar And Its Application In The Detection Of Estrogens Content In Food

Food safety is a growing concern.Humans were affected by the accumulation of estrogens in food throughout the food chain.However,estrogens are found in trace amounts in actual samples and complex matrices,so selecting a suitable sample pretreatment method becomes the most critical issue.Stir Bar Sorptive Extraction（SBSE）,a novel and miniature sample pretreatment technique,is not only simple,convenient,green,and efficient,but also can be used in conjunction with high-performance liquid chromatography（HPLC）,gas chromatography,and gas chromatography.SBSE has been widely used in food,environmental and biological fields.However,the commercial stir bar coatings for SBSE are relatively few and limited in application,so new stir bar coatings should be explored and developed.Covalent organic framework polymers（COFs）with low density,good stability,large specific surface area,and adjustable pore structure can adsorb estrogens in food.Based on this,this paper synthesized a variety of COFs materials simply and rapidly at room temperature and prepared COFs coated stir bar.Estrogens in food were detected by SBSE and HPLC.A series of characterizations of COFs materials were carried out.The extraction efficiency of different COFs coated stirring bars on estrogens was compared.The relationship between the structure of COFs coating and the sorptive extraction of estrogens was investigated.The main studies are as follows:（1）TAPM-TA-COF was synthesized with tris（4-aminophenyl）methane and terephthalaldehyde at room temperature.At room temperature,TAPA-TA-COF was synthesized with tris（4-aminophenyl）amine and terephthalaldehyde.TPAs-3NH₂-TA-COF was synthesized with N4,N4-bis（4’-amino-[1,1’-biphenyl]-4-yl）-[1,1’-biphenyl]-4,4’-diamine and terephthalaldehyde at room temperature.The three COFs materials were labeled as COF-a,COF-b,and COF-c.The COFs coated stir bar was prepared by the physical coating method.The conditions of SBSE were optimized to establish a new COF-HPLC-DAD method for analyzing trace estrogens in meat foods.The conditions of SBSE were optimized with COF-b coated stir bar:extraction time of 30 min,stirring rate of 700 rpm,adsorbent of 200μL acetone/10 m M Na OH（v/v,8/2）,desorption time of 20 min,Na Cl concentration of 5%（m/v）and p H of 7.Under these conditions,the extraction of COF-a-SBSE-LD-HPLC-DAD,COF-b-SBSE-LD-HPLC-DAD,and COF-c-SBSE-LD-HPLC-DAD methods were evaluated for their performance.The RSDs of COF-a-SBSE-LD-HPLC-DAD were 6.5-8.3%（n=10,c=10μg/L）,the enrichment folds were 17.0-38.4,and the four estrogens in the range of 0.1-0.2μg/L.COF-b-SBSE-LD-HPLC-DAD with RSDs of 4.5-9.1%（n=10,c=10μg/L）,enrichment ploidy of 16.7-46.4-fold,and detection limits of 0.1-0.15μg/L for the four estrogens.The RSDs of COF-c-SBSE-LD-HPLC-DAD was 5.8-9.8%（n=10,c=10μg/L）,the enrichment folds were 32.8-49.8,and the detection limits of the four estrogens were in the range of 0.1-0.2μg/L.The stir bar coated with COF-c in combination with HPLC showed the highest enrichment folds for the four estrogens.（2）TAPB-TA-COF was synthesized with 1,3,5-tris（4-aminophenyl）benzene and terephthalaldehyde at room temperature.TAPP-TA-COF was synthesized with 2,4,6-tris（4-aminophenyl）pyridine and terephthalaldehyde.TAPT-TA-COF was synthesized with 1,3,5-tris（4-aminophenyl）triazine and terephthalaldehyde at room temperature.The three COFs materials were labeled as COF-d,COF-e,and COF-f,respectively.The COFs-coated stir bar was prepared by the physical coating method.The conditions of SBSE were optimized to establish a COF-HPLC-DAD method for the analysis of trace estrogens in dairy products.The SBSE conditions were optimized with COF-f coated stir bar as the mainstay:extraction time of 30 min,stirring rate of 700 rpm,adsorbent of 200μL acetone/10 m M Na OH（v/v,9/1）,desorption time of 20 min,Na Cl concentration of 10%（m/v）,p H of 7.Under these conditions,the extraction of COF-d-SBSE-LD-HPLC-DAD,COF-e-SBSE-LD-HPLC-DAD,and COF-f-SBSE-LD-HPLC-DAD methods were evaluated.The RSDs of COF-d-SBSE-LD-HPLC-DAD was 4.4-8.9%（n=10,c=10μg/L）,the enrichment folds were 15.9-37.7,and the four estrogens in the range of 0.1-0.2μg/L.The RSDs of COF-e-SBSE-LD-HPLC-DAD was 4.8-8.7%（n=10,c=10μg/L）,the enrichment ploidy was 16.6-40.5-fold,and the detection limits of the four estrogens were 0.1-0.2μg/L.The RSDs of COF-f-SBSE-LD-HPLC-DAD was 5.7-8.6%（n=10,c=10μg/L）,the enrichment ploidy was 17.2-42.3-fold,and the detection limits of the four estrogens were 0.1-0.15μg/L.The stir bar coated with COF-f in combination with HPLC showed the highest enrichment folds for the four estrogens.